Liquid crystal display and a method for fabricating the same

ABSTRACT

A liquid crystal display includes first and second substrates. The first substrate has a first insulating substrate, and a pixel electrode formed on the first insulating substrate with a first opening pattern. The second substrate has a second insulating substrate, and a common electrode formed on the second insulating substrate with a second opening pattern. The first and the second opening patterns proceed parallel to each other while being arranged in an alternate manner. A liquid crystal material is injected between the first and the second substrates. A spacer is positioned at an end of the second opening pattern to maintain the distance between the first and the second substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.11/313,965 filed on Dec. 22, 2005, which is a Continuation of U.S.patent application Ser. No. 09/928,349 filed on Aug. 14, 2001 whichissued as U.S. Pat. No. 7,057,695, which claims priority to and thebenefit of Korean Patent Application Nos. 10-2001-47489 filed on Aug. 7,2001; 10-2001-0047318 filed on Aug. 6, 2001; 10-2001-001791 filed onJan. 12, 2001; 10-2000-0047001 filed on Aug. 14, 2000, the disclosuresof which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display and a methodfor fabricating the same and, more particularly, to a liquid crystaldisplay that has spacers for maintaining the gap between two substrates.

(b) Description of the Related Art

Generally, a liquid crystal display has a structure where a liquidcrystal bearing dielectric anisotropy is sandwiched between a colorfilter substrate and a thin film transistor array substrate. The colorfilter substrate has a common electrode, a color filter and a blackmatrix, and the thin film transistor array substrate has a thin filmtransistor and a pixel electrode. An electric field is applied to theliquid crystal, thereby controlling the light transmission anddisplaying the desired picture image.

In order to obtain a wide viewing angle, such a liquid crystal displayuses a mode of patterned vertical alignment (PVA) having multipledomains. In the PVA mode, opening patterns or protrusions are made atthe pixel electrode and the common electrode while forming fringe fieldsthere. These fringe fields make the liquid crystal molecules to beinclined in various directions, thereby realizing wide viewing angle.

Meanwhile, in order to maintain the gap between the two substrates in aconstant manner, elastic spacers are disposed between them. However,when an external impact is applied to the liquid crystal display, thegap between the substrates is seriously deformed due to the elasticityof the spacers, causing spots on the screen.

Furthermore, a separate process should be made to form such spacers, andthis deteriorates the production efficiency.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a liquid crystaldisplay that minimizes variation in the brightness while enhancing thepicture quality.

It is another object of the present invention to provide a method forfabricating a liquid crystal display in simplified processing steps.

These and other objects may be achieved by a liquid crystal display withthe following features.

According to one aspect of the present invention, the liquid crystaldisplay includes first and second substrates. The first substrate has afirst insulating substrate, and a pixel electrode formed on the firstinsulating substrate with a first opening pattern. The pixel electrodehas upper and lower half regions, upper and lower sides, and left andright sides. The second substrate has a second insulating substrate, anda common electrode formed on the second insulating substrate with asecond opening pattern. The first and the second opening patternsproceed parallel to each other while being arranged in an alternatemanner. A liquid crystal material is injected between the first and thesecond substrates. A spacer is positioned at an end of the secondopening pattern to maintain the distance between the first and thesecond substrates.

The first opening pattern has a first opening portion positioned at theupper half region of the pixel electrode while proceeding in a firstdirection, and a second opening portion positioned at the lower halfregion of the pixel electrode while proceeding in a second direction.The first and the second directions are perpendicular to each other. Thesecond opening pattern has a first trunk opening portion positioned at aregion of the common electrode corresponding to the upper half region ofthe pixel electrode while proceeding in the first direction, and asecond trunk opening portion positioned at another region of the commonelectrode corresponding to the lower half region of the pixel electrodewhile proceeding in the second direction.

The first direction proceeds in a slant manner with respect to the sidesof the pixel electrode.

The second opening pattern further has a first branch opening portionoverlapping the upper and lower sides of the pixel electrode, and asecond branch opening portion overlapping the left and right sides ofthe pixel electrode. The first opening pattern further has a thirdopening portion positioned between the upper and the lower half regionsof the pixel electrode while proceeding parallel to the upper and lowersides of the pixel electrode. The first and the second opening patternsdivide the pixel electrode into a plurality of closed polygons.

The second branch opening portion has an opening width larger than thefirst trunk opening portion. The first direction proceeds parallel toone of the sides of the pixel electrode.

According to another aspect of the present invention, the liquid crystaldisplay includes first and second substrates. The first substrate has afirst insulating substrate, and a pixel electrode formed on the firstinsulating substrate with a first opening pattern. The pixel electrodehas a first side and a second side facing the first side. The firstopening pattern has a first opening portion proceeding from the firstside of the pixel electrode in the horizontal direction, and second andthird opening portions proceeding from the first side of the pixelelectrode to the second side in a slant manner symmetrical to each otherwith respect to the first opening portion while being gradually reducedin distance from each other. The second substrate has a secondinsulating substrate facing the first insulating substrate, and a commonelectrode formed on the second insulating substrate with a secondopening pattern. The first and the second opening patterns are arrangedin an alternate manner. The second opening pattern has fourth to sixthopening portions. The fourth opening portion has a trunk proceeding inthe horizontal direction, first and second branches proceeding from thetrunk in a slant manner while being gradually increased in distance fromeach other, and first and second sub-branches extended from the firstand the second branches in the vertical direction while proceedingopposite to each other. The fifth opening portion has a first baseproceeding parallel to the first branch, and first and second limbsextended from both ends of the first base in the horizontal directionand in the vertical direction. The sixth opening portion proceedssymmetrical to the fifth opening portion with respect to the fourthopening portion. A liquid crystal material is injected between the firstand the second substrates. A spacer is positioned at an end of thesecond opening pattern to maintain the distance between the first andthe second substrates.

According to still another aspect of the present invention, the liquidcrystal display has first and second substrates. The first substrate hasa first insulating substrate, and a pixel electrode formed on the firstinsulating substrate with a first opening pattern. The pixel electrodehas upper and lower half regions. The first opening pattern has a firstopening portion vertically partitioning the upper half region of thepixel electrode, and a second opening portion horizontally partitioningthe lower half region of the pixel electrode. The second substrate has asecond insulating substrate facing the first insulating substrate, and acommon electrode formed on the second insulating substrate with a secondopening pattern. The second opening pattern has a third opening portionproceeding in the vertical direction, and a fourth opening portionproceeding in the horizontal direction below the third opening portion.The first and the third opening portions are arranged in an alternatemanner while vertically partitioning the upper half region of the pixelelectrode into a plurality of micro-regions. The second and the fourthopening portions are arranged in an alternate manner while horizontallypartitioning the lower half region of the pixel electrode into aplurality of micro-regions. A liquid crystal material is injectedbetween the first and the second substrates. A spacer is providedbetween the two substrate to maintain the distance between them.

According to still another aspect of the present invention, a colorfilter substrate for the liquid crystal display includes an insulatingsubstrate, a black matrix formed on the insulating substrate, a colorfilter formed at the black matrix, a common electrode formed on theentire surface of the common electrode, and first and second protrusionsformed on the common electrode. The first protrusion has a firstthickness, and the second protrusion has a second thickness greater thanthe first thickness.

The first and the second protrusions are formed with one or more of aphotosensitive organic insulating layer, a photoresist film, and asilicon-based insulating layer. The common electrode is formed withindium tin oxide or indium zinc oxide.

According to still another aspect of the present invention, in a methodfor fabricating a color filter substrate for the liquid crystal display,a black matrix is first formed on an insulating substrate. A colorfilter is then formed on the black matrix. A common electrode is formedon an entire surface of the insulating substrate. An insulating layer isdeposited onto the common electrode. The insulating layer is thenpatterned to thereby form a first protrusion with a first thickness, anda second protrusion with a second thickness greater than the firstthickness.

The insulating layer is formed with one or more of a photosensitiveorganic insulating layer, a photoresist film, and a silicon-basedinsulating layer. The common electrode is formed with indium tin oxideor indium zinc oxide.

The insulating layer may be formed with a negative photosensitiveorganic insulating material. In this case, the first and the secondprotrusions are formed through a mask with a slit pattern correspondingto the first protrusion, and a transparent pattern corresponding to thesecond protrusion.

Alternatively, the insulating layer may be formed with a negativephotosensitive organic insulating material. In this case, the first andthe second protrusions are formed through a mask with a semitransparentpattern corresponding to the first protrusion, and an opaque patterncorresponding to the second protrusion.

A photoresist pattern of different in thickness may be formed on theinsulating layer through one photolithography process.

According to still another aspect of the present invention, in a methodfor fabricating the liquid crystal display, a thin film transistor arraysubstrate is first formed such that the thin film transistor arraysubstrate has a pixel electrode with a wiring line pattern, a switchingcircuit and an opening pattern. A color filter substrate is then formedsuch that the color filter substrate has a common electrode, a colorfilter, a high molecular pillar, and a protrusion pattern. The thin filmtransistor array substrate is combined with the color filter substrate,and a liquid crystal material is injected between the thin filmtransistor array substrate and the color filter substrate.

According to still another aspect of the present invention, in a methodfor fabricating a color filter substrate for the liquid crystal display,a black matrix and a color filter are formed on a transparent substratein a sequential manner. An over-coat layer is formed on the color filtersubstrate. A common electrode is formed on the over-coat layer with atransparent conductive material. A photosensitive resin is coated ontothe common electrode. The photosensitive resin is then exposed to lightthrough a mask, and developed to thereby form a protrusion and a highmolecular pillar of different height. The mask has a first pattern withan opening width smaller than the resolution of the light exposingdevice, and a second pattern with an opening width larger than theresolution of the light exposing device.

The protrusion has a width of 4-14 μm, and the high molecular pillar hasa width of 15-45 μm. The protrusion has a height of 1.0-1.2 μm, and thehigh molecular pillar has a height of 3.0-4.5 μm.

The protrusion and the high molecular pillar may go through hard bakingat a predetermined temperature such that the protrusion and the highmolecular pillar bear a predetermined strength. The height of theprotrusion and the high molecular pillar can be controlled throughvarying the hard baking temperature. The hard baking temperature is inthe range of 200-240° C.

According to still another aspect of the present invention, a thin filmtransistor array substrate for the liquid crystal display includes agate line assembly with a gate electrode and a gate line, and a dataline assembly with a data line crossing over the gate line, a sourceelectrode, and a drain electrode. A semiconductor pattern contacts thesource and the drain electrodes while forming a thin film transistortogether with the gate electrode, the source electrode, and the drainelectrode. An organic insulating pattern is formed on the semiconductorpattern. The organic insulating pattern has a protrusion pattern with afirst thickness, a contact hole exposing the drain electrode, and a flatportion with a second thickness. A pixel electrode is formed on theorganic insulating pattern while being connected to the drain electrodethrough the contact hole.

The semiconductor pattern is formed with hydrogenated amorphous silicon.The semiconductor pattern has the same shape as the data line assemblyexcept that the semiconductor pattern further has a channel regionbetween the source and the drain electrodes. The semiconductor patternis formed over the gate electrode with an island shape.

According to still another aspect of the present invention, in a methodfor fabricating the thin film transistor array substrate, a gate lineassembly is formed on a substrate with a gate line and a gate electrode.A gate insulating layer is formed on the substrate such that the gateinsulating layer covers the gate line assembly. A semiconductor patternis formed on the gate insulating layer. A data line assembly is formedon the gate insulating layer and the semiconductor pattern with a dataline, a source electrode, and a drain electrode. An organic insulatingpattern is formed on the semiconductor pattern such that the organicinsulating pattern has a protrusion pattern with a first thickness, acontact hole exposing the drain electrode, and a flat portion with asecond thickness. A pixel electrode is formed on the organic insulatingpattern such that the pixel electrode is connected to the drainelectrode through the contact hole.

The organic insulating pattern is formed through the steps of forming aphotosensitive organic insulating layer on an entire surface of thesubstrate with the data line assembly, exposing the photosensitiveorganic insulating layer in a selective manner such that thephotosensitive organic insulating layer has a first portion interceptedfrom light where the protrusion pattern is formed, a second portionentirely exposed to light where the contact hole is formed, and a thirdportion partially exposed to light, and developing the selectivelylight-exposed organic insulating layer.

The step of selectively exposing the organic insulating layer to lightis made through a mask with a light intercepting region placed over thefirst portion of the organic insulating layer, a light transmittingregion placed over the second portion of the organic insulating layer,and a selectively light transmitting region placed over the third regionwhile bearing a predetermined light transmission.

Alternatively, the step of selectively exposing the organic insulatinglayer to light may be made through a first mask for exposing the secondportion of the organic insulating layer to light, and a second mask forexposing the third portion of the organic insulating layer to light witha predetermined light transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or the similar components.

FIG. 1 is a schematic view of a liquid crystal display according to afirst preferred embodiment of the present invention.

FIG. 2 is a schematic view of a liquid crystal display according to asecond preferred embodiment of the present invention.

FIG. 3 is a schematic view of a liquid crystal display according to athird preferred embodiment of the present invention.

FIG. 4 is a sectional view of a liquid crystal display according to afourth preferred embodiment of the present invention.

FIGS. 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14 sequentially illustrate thesteps of fabricating a color filter substrate for the liquid crystaldisplay shown in FIG. 4.

FIGS. 15A, 15B; 16A, 16B, 17A, 17B, 18A, 18B, 19A, 19B, 20A, 20B, 21,22, 23A and 23B illustrate the steps of fabricating a thin filmtransistor array substrate and a color filter substrate for a liquidcrystal display according to a fifth preferred embodiment of the presentinvention

FIG. 24 is a graph illustrating the variation in height of aphotosensitive resin pattern remaining after the photolithographyprocess as a function of pattern width and hard baking temperature.

FIG. 25 is an electron microscope photograph of a photosensitive resinremaining after the photolithography process.

FIG. 26 is a conceptual view for mathematically inducing the sectionalvolume, width, and breadth of the photosensitive resin shown in FIG. 25.

FIG. 27 is a conceptual view illustrating the sectional profile of aphotosensitive resin after the hard baking process,

FIG. 28 is a graph illustrating the variation in height H of aphotosensitive resin as a function of pattern width,

FIG. 29 is a plan view of a thin film transistor array substrate for aliquid crystal display according to a sixth preferred embodiment of thepresent invention.

FIG. 30 is a cross sectional view of the thin film transistor arraysubstrate taken along the XXX-XXX′ line of FIG. 29.

FIGS. 31A, 31B, 32A, 32B, 33A, 33B, 34A, 34B and 35 illustrate the stepsof fabricating the thin film transistor array substrate shown in FIG.29.

FIG. 36 is a plan view of a thin film transistor array substrate for aliquid crystal display according to a seventh preferred embodiment ofthe present invention.

FIGS. 37 and 38 are cross sectional views of the thin film transistorarray substrate taken along the XXXVII-XXXVII′ line and theXXXVIII-XXXVIII′ line of FIG. 36,

FIGS. 39A, 39B, 39C, 40A, 40B, 40C, 41A, 41B, 42A, 42B, 43A, 43B, 44A,44B, 45A, 45B, 46A, 46B, 46C, 47A and 47B illustrate the steps offabricating the thin film transistor array substrate shown in FIG. 36.

FIG. 48 is a plan view of a thin film transistor array substrate for aliquid crystal display according to an eighth preferred embodiment ofthe present invention.

FIG. 49 is a cross sectional view of the thin film transistor arraysubstrate taken along the XXXXIX-XXXXIX′ line of FIG. 48.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with referenceto the accompanying drawings.

FIG. 1 is a schematic view of a liquid crystal display according to afirst preferred embodiment of the present invention.

The liquid crystal display includes bottom and top substrates 1000 and2000 arranged in parallel while facing each other, a liquid crystallayer 310 with liquid crystal molecules 300 sandwiched between the twosubstrates 1000 and 2000, and spacers 100 disposed between thesubstrates 1000 and 2000 to keep the inter-substrate distance constant.The liquid crystal molecules 300 are vertically aligned with respect tothe substrates 1000 and 2000.

The bottom substrate 1000 is formed with a first insulating substrate10, and pixel electrodes 80 internally placed on the first insulatingsubstrate 10. The first insulating substrate 10 is formed of atransparent insulating material such as glass, and the pixel electrode80 is formed of a transparent conductive material such as indium tinoxide (ITO) and indium zinc oxide (IZO). The pixel electrode 80 has anopening pattern (not shown), and is connected to a switching circuit 11to receive picture signal voltages.

An alignment layer 90 is formed on the first insulating substrate 10with the pixel electrodes 80 to align the liquid crystal molecules 300.A thin film transistor is used for the switching circuit 11. The thinfilm transistor is connected to a gate line (not shown) for transmittingscanning signals, and to a data line (not shown) for transmittingpicture signals, respectively. The thin film transistor turns on or offin accordance with the scanning signals.

A bottom polarizing plate 14 is externally attached to the bottomsubstrate 1000. In a reflection type liquid crystal display, the pixelelectrode 80 may be formed of a non-transparent material. In this case,the bottom polarizing plate 14 may be omitted.

The top substrate 2000 is formed of a second insulating substrate 200, ablack matrix 210, color filters 220 of red, green and blue, a commonelectrode 230, and an alignment layer 250. The black matrix 210 preventslight leakage. The alignment layer 250 aligns the liquid crystalmolecules 300. The common electrode 230 is formed with a transparentconductive material such as ITO and IZO while bearing an opening pattern(or a protrusion) (not shown). Alternatively, the black matrix 210 andthe color filters 220 may be formed at the bottom substrate 1000. A toppolarizing plate 400 is externally attached to the top substrate 2000.

The polarizing directions of the bottom and the top polarizing plates 14and 400 are perpendicular to each other in a normally black mode,whereas those are in parallel to each other in a normally white mode. Inthis preferred embodiment, only the normally black mode is considered asexample.

FIG. 2 illustrates the structure of a liquid crystal display accordingto a second preferred embodiment of the present invention.

As shown in FIG. 2, a bottom substrate with a pixel electrode and a topsubstrate with a common electrode are arranged in parallel. Each of thepixel electrode and the common electrode is provided with an openingpattern (or an protrusion).

A gate line assembly is formed on the bottom substrate. The gate lineassembly includes gate lines 22 for transmitting gate signals, and gateelectrodes 26 connected to the gate lines 22 to form a thin filmtransistor together with other components.

Furthermore, a data line assembly is formed on the bottom substrate. Thedata line assembly includes data lines 62 for transmitting data signalswhile crossing over the gate lines 22 to define pixels, sourceelectrodes 65 connected to the data lines 62 to function as a part ofthe thin film transistor, and drain electrodes 66 facing the sourceelectrodes 65 around the gate electrodes 26. A pixel electrode 80 iselectrically connected to the drain electrode 66 to receive the datasignals.

Furthermore, storage capacitor lines 27 and 28 are placed around theperiphery of the unit pixel and overlap the pixel electrode 80 to form astorage capacitor. The storage capacitor lines 27 and 28 prevent lightleakage at the periphery of the unit pixel.

As shown in FIG. 2, the pixel electrode 80 is provided with a firstopening portion 821. The first opening pattern 821 tapers from the leftside to the right at the center of the pixel electrode 80. The edges ofpixel electrode 80 from which the first opening pattern 821 proceeds arecut off, and smoothly curved.

A second opening portion 822 and a third opening portion 823 are formedat the upper half region and the lower half region of the pixelelectrode 80 around the first opening portion 821. The second openingportion 822 and the third opening portion 823 diagonally proceed at theupper region and the lower region of the pixel electrode 80symmetrically. The second opening portion 822 and the third openingportion 823 proceed from the right side to the left side at the upperregion and the lower region of the pixel electrode 80 while graduallyapproaching the first opening portion 821.

The pixel electrode 80 is protruded to the outside at the area where thesecond opening portion 822 and the third opening portion 823 areterminated. It is protruded to prevent failure in the interconnection ofthe respective portions of the pixel electrode 80 due to the openingportions 822 and 823.

Meanwhile, fourth, fifth and sixth opening portions (or first, secondand third protrusion portions) are formed at the common electrode 230.The fourth opening portion (or first protrusion portion) includes atrunk 211 proceeding in the horizontal direction, and a first body 212and a second body 214 that obliquely extended from the trunk 211 upwardand downward, and a first branch 213 and a second branch 215 thatextended along the pixel electrode from the first body 212 and thesecond body 214 upward and downward.

The fifth opening portion (or second protrusion portion) includes athird body 221 proceeding slantingly parallel to the first body 212, athird horizontal branch 222 proceeding along the pixel electrode fromthe third body 221 in the horizontal direction, a third vertical branch223 proceeding along the pixel electrode from the third body 221 in thevertical direction. The sixth opening portion (or third protrusionportion) includes a fourth body 231 proceeding slantingly parallel tothe second body 214, a fourth horizontal branch 232 proceeding along thepixel electrode from the fourth body 231 in the horizontal direction, afourth vertical branch 233 proceeding along the pixel electrode from thefourth body 231 in the vertical direction. That is, the fifth and thesixth opening portions (or second and third protrusion portions) areformed at the upper half region and the lower half region of the unitpixel of the common electrode 230 symmetrical to each other. The fourth,the fifth and the sixth opening portions (or first, second and thirdprotrusion portions) are repeatedly formed at the respective pixels ofthe common electrode 230. As shown in FIG. 2, a second opening 822 issubstantially orthogonal to a third opening 823, and at least oneopening (or at least one protrusion) (212, 214, 221, 231) which isformed at the common electrode includes a branch (213, 215, 222, 223,232, 233) that meets at an acute angle with an end portion of at leastone of the openings (822, 823).

As shown in FIG. 2, the first opening portion 821, the second openingportion 822 and the third opening portion 823 of the pixel electrode 80are overlapped with the fourth, fifth and sixth opening portions (or thefirst, second and third protrusion portions) of the common electrode 230such that the pixel electrode area is divided into several domains. Theopening portions of the pixel electrode 80 and the opening portions (orprotrusion portions) of the common electrode 230 are arranged in analternate manner while proceeding in parallel.

In this structure, under the application of an electric field, theliquid crystal molecules at one unit pixel are aligned in fourdirections along the directions of the fringe fields due to the openingportions. Therefore, wide viewing angle can be obtained in fourdirections.

Spacers 100 are formed at the ends of the opening portions (orprotrusion portions) of the common electrode 230 of an organic materialto maintain the distance between the two substrates constant. Thespacers 100 prevent disclination at the ends of the opening portions (orprotrusion portions) where the directors of the liquid crystal moleculesare not oriented uniformly.

When driving voltages are applied to the pixel electrode 80 and thecommon electrode 230, electric fields are not uniformly formed at theends of the opening portions (or protrusion portions) so that theinclination of the electric field is seriously changed while breakingoff the normal orientation of the liquid crystal molecules.

The spacers made of an organic material can prevent the disclinationwhile maintaining the distance between the two substrates even when anexternal impact is applied, thereby preventing deterioration of thebrightness.

The opening patterns (or the protrusions) may bear various shapes tomake partitioned areas of different orientations of the liquid crystalmolecules, but they usually meet the following requirements.

First, in order to obtain the best viewing angle, it is preferable thatfour-partitioned regions should be placed within one pixel.

Second, in order to obtain stable orientation of the liquid crystalmolecules, disclination or non-uniform texture should not be generatedat the outside of the partitioned micro-regions. Disclination is madewhere the directors of the liquid crystal molecules are oriented invarious directions, and particularly where the liquid crystal moleculesat one region are inclined against one another. Therefore, in order toachieve stable partitioned-orientation, the opening patterns (or theopening patterns and protrusions) of the top and the bottom substratesare alternately arranged while being close to each other at the endportions thereof.

That is, when viewed from the top, the region surrounded by the openingpatterns (or the opening patterns and the protrusions) of the top andthe bottom substrates should bear a shape of closed polygons. Meanwhile,in case the opening pattern (or protrusion) has edges of acute angle,disclination is liable to occur. Thus, the opening pattern (orprotrusion) should be formed at an obtuse angle. Stablepartitioned-orientation also influences the brightness. In the regionsof scattered orientation, light leaks at an off state, and a darkerimage is displayed at an on-state compared to other regions. When theorientation of the liquid crystal molecules changes, the regions ofscattered orientation float and cause afterimages.

Third, in order to obtain high brightness, the following conditionsshould be met. The angle between the directors of the liquid crystalmolecules at the neighboring regions should be 90°. In this state,disclination is made at the narrowest region. Also, when the anglebetween the light transmission axis of the polarizing plate and thedirector of the liquid crystal molecule is 45°, the highest brightnesscan be obtained.

Finally, in order to obtain a rapid response speed, it is preferablethat the opening patterns (or protrusions) of the top and bottomsubstrates should not be much bent or curved.

FIG. 3 is a schematic view of a liquid crystal display according to athird preferred embodiment of the present invention.

As shown in FIG. 3, the structure of the gate and data line assembliesis the same as that of the second preferred embodiment.

Storage capacitor lines 27, 28 and 29 are formed at the periphery of theunit pixel as well as at the area where the opening portions 111 and 112of the pixel electrode 80 are placed.

The pixel electrode 80 has a first opening portion 111 placed at theupper half region thereof in the vertical direction, and a secondopening portion 112 placed at the lower half region thereof in thehorizontal direction. The first opening portion 111 divides the pixelelectrode 80 into two left and right regions. The second opening pattern112 divides the lower half region of the pixel electrode 80 into fourmicro-regions.

A third opening portion (or a first protrusion portion) is formed at theunit pixel of the common electrode 230. The third opening portion (orthe first protrusion portion) includes a first linear element 241 and asecond linear element 242 vertically arranged parallel to each other,and a third linear element 243 proceeding in the horizontal directionwhile dividing the unit pixel of the common electrode 230 into two upperand lower regions.

Furthermore, a fourth opening portion (or a second protrusion portion)244 and a fifth opening portion (or a third protrusion portion) 245 areformed at the lower pixel region of the common electrode 230 whilehorizontally proceeding parallel to each other. The ends of the thirdthrough the fifth opening portions (or protrusion portions) 241 through245 are gradually enlarged in width while forming a triangle shape.

As shown in FIG. 3, the first opening portion 111 and the first linearelement 241 and the second linear element 242 of the third openingportion (or first protrusion portion) are alternately arranged inparallel at their centers while vertically partitioning the upper regionof the pixel electrode 80 into four micro-regions. The second openingportion 112, the third linear element 243 of the third opening portion(or first protrusion portion), and the fourth and the fifth openingportions (or the second and the third protrusion portions) 244 and 245are alternately arranged in parallel at their centers while horizontallypartitioning the lower region of the pixel electrode 80 into sixmicro-regions.

Spacers 100 are formed at the ends of the opening portions or protrusionportions of the common electrode 230 between the neighboring pixels withan organic material. These spacers 100 have the same function aspreviously described in the first preferred embodiment.

Alternatively, it is possible that an opening pattern is formed at thecommon electrode, and protrusions are formed at the pixel electrodetogether with an opening pattern. In this case, the protrusions may beformed together with a gate insulating layer or a protective layer. Itshould be noted in forming such protrusions that a parasitic staticcapacitance may be formed between the protrusions and the neighboringlines. It is also possible that an opening pattern is formed at thepixel electrode, whereas protrusions are formed at the common electrode.

As described above, in the liquid crystal display according to thefirst, second and third preferred embodiments, organic material-basedspacers may be formed at the desired place to maintain the distancebetween the substrates in a constant manner, preventing disclination aswell as the brightness deterioration.

FIG. 4 is a sectional view of a liquid crystal display according to afourth preferred embodiment of the present invention where a thin filmtransistor array substrate and a color filter substrate are arrangedwhile facing each other.

As shown in FIG. 4, the thin film transistor array substrate 1000 has afirst insulating substrate 10, a thin film transistor 11 formed on thefirst insulating substrate 10, and a pixel electrode 80 electricallyconnected to the thin film transistor 11 while bearing an openingpattern 6. The color filter substrate 2000 has a second insulatingsubstrate 200, a black matrix 210, color filters 220, and a commonelectrode 230.

In the color filter substrate 2000, the black matrix 210 is formed onthe second insulating substrate 200, and the color filters 220 of red,green and blue are surrounded by the black matrix 210. The commonelectrode 230 is formed on the entire surface of the substrate 200 withindium tin oxide (ITO) or indium zinc oxide (IZO) while covering theblack matrix 210 and the color filters 220. The portion of the commonelectrode 230 placed on the black matrix 210 is sunken compared to thatplaced on the color filter 220. First photosensitive organic insulatingpatterns (that is, protrusions) 160 and second photosensitive organicinsulating patterns (that is, spacers) 170 are formed on the commonelectrode 230. The first and second organic insulating patterns 160 and170 have different thickness. The first organic insulating pattern(protrusion) 160 over the color filter 220 are thinner than the secondorganic insulating pattern (spacers) 170 over the black matrix 210.

In the thin film transistor array substrate, the pixel electrode 80 isformed on the first insulating substrate 10 while bearing an openingpattern 6. The thin film transistor 11 is also formed on the firstinsulating substrate 10 to switch the signals applied to the pixelelectrode 80. A drain electrode is electrically connected to the pixelelectrode 80 as a part of the thin film transistor 11.

Under the application of voltage to the common electrode 230 and thepixel electrode 80, fringe fields f shown in FIG. 4 are formed. Theliquid crystal molecules 40 are oriented in four directions due to thefringe fields so that the desired multi-domains can be obtained withoutpatterning the common electrode 230.

The organic insulating patterns 160 and 170 may be formed with aphotosensitive organic insulating material, a positive or negativephotosensitive material, or a silicon-based insulating material.

The fringe fields f are formed by way of the second organic insulatingpattern 160 bearing a thin thickness while forming multiplemicro-regions, resulting in wide viewing angle. The first organicinsulating pattern 170 positioned corresponding to the thin filmtransistor 11 functions as a spacer for maintaining the gap between thesubstrates 1000 and 2000 called the “cell gap.” As the thickness of thecell gap is at best 3-4 μm, the response speed can be enhanced.

Furthermore, the second organic insulating pattern 160 for forming thefringe field f and the first organic insulating pattern 170 used for thespacer are formed through one photolithography process, therebysimplifying the number of processing steps.

A method for fabricating the color filter substrate will be nowexplained with reference to FIGS. 5 through 14.

First, as shown in FIG. 5, a black matrix 210 is formed on an insulatingsubstrate 200, and color filters 220 of red, green and blue are formedat the black matrix 210.

Then, as shown in FIG. 6, a common electrode 230 is formed on the entiresurface of the substrate 200 with a transparent conductive material suchas ITO and IZO such that it covers the black matrix 210 and the colorfilters 220.

As shown in FIG. 7, a photosensitive organic insulating layer 150 isdeposited onto the common electrode 230. At this time, a negative orpositive photosensitive layer, or a silicon-based insulating layer maybe deposited onto the common electrode 230 instead of the photosensitiveorganic insulating layer 150.

As shown in FIG. 8, the photosensitive organic insulating layer 150 ispatterned through a mask to thereby form photosensitive organicinsulating patterns 160 and 170. The resulting photosensitive organicinsulating patterns 160 and 170 have different thickness. It ispreferable that the mask should bear a slit pattern or a semitransparentfilm.

A method for forming such organic insulating patterns using a mask witha slit pattern will be now explained with reference to FIGS. 8 and 9.

Either a negative photosensitive material or a positive photosensitivematerial may be used to form the organic insulating layer. In case anegative photosensitive material is used for the organic insulatinglayer, only the light-exposed portions of the organic insulating layerare left over after the development.

As shown in FIG. 9, the mask M1 includes a slit pattern placed at the Barea over the color filter 220, a transparent pattern placed at the Aarea over the black matrix A, and an opaque pattern at the remaining Carea.

When the light exposing is made using such a mask M1, larger amount oflight passes the transparent pattern than the slit pattern. Therefore,when the photosensitive organic insulating layer 150 is light-exposedand developed, as shown in FIG. 8, the thickness of the negative organicinsulating layer 160 remaining at the B area is thinner than thenegative organic insulating layer 170 remaining at the A area, and thenegative organic insulating film 160 is absent at the C area.

In the case for an organic insulating layer bearing a negativephotosensitivity, the upper side thereof becomes wider than the lowerside thereof after the development while forming a counter-taperingshape. But, in the subsequent processing steps, the upper side of theorganic insulating layer is reduced in thickness while forming aperpendicularly proceeding pattern.

A method of forming organic insulating patterns using a mask with asemitransparent film will be now explained with reference to FIGS. 8 and10.

Either a negative photosensitive material or a positive photosensitivematerial may be used to form an organic insulating layer. In case theorganic insulating layer is formed with a positive photosensitivematerial, the light-exposed portions thereof are removed after thedevelopment.

As shown in FIG. 10, the mask M2 includes a semitransparent film placedat the B area over the color filter 220, an opaque pattern placed at theA area over the black matrix 210, and a transparent pattern placed atthe remaining C area.

When the substrate is exposed to light using the mask M2, larger amountof light passes the transparent pattern than the semitransparentpattern. Therefore, when the organic insulating layer is light-exposedand developed, the positive organic insulating layer remaining at the Barea is thinner than the positive organic insulating layer remaining atthe A area, and the positive organic insulating layer is absent at the Carea.

If a negative organic insulating layer that leaves the light-exposedportions after the development is used to form the organic insulatingpatterns, it becomes difficult to make the portions covered by thesemitransparent film have the desired thickness after the development.Thus, it is advantageous to use a positive organic insulating layer informing the organic insulating patterns.

In this way, the organic insulating patterns 160 and 170 of differentthickness are formed using the mask with a slit pattern or asemitransparent film. The thin organic insulating pattern 160 is used toform fringe fields. The thick organic insulating pattern 170 is used fora spacer.

As described above, the organic insulating patterns 160 and 170 ofdifferent thickness are formed through one photolithography process,which minimizes the number of relevant processing steps.

Meanwhile, a silicon-based insulating layer may be used instead of thephotosensitive organic insulating layer. In this case, a silicon-basedinsulating layer is deposited onto the substrate, and a photoresist filmis coated onto the insulating layer. The substrate with the insulatinglayer and the photoresist film goes through the photolithography processusing a mask with a slit pattern or a semitransparent film. In thispreferred embodiment, a negative photosensitive film is used for thephotoresist film.

As shown in FIG. 11, a photoresist film 152 is coated onto asilicon-based insulating layer 151, and patterned through a mask M3 tothereby form photoresist patterns 116 and 117. As shown in FIG. 12, thephotoresist patterns 116 and 117 have different thickness.

The mask M3 includes a slit pattern placed at the B area, an opaquepattern placed at the A area, and a transparent pattern placed at the Carea. When the photoresist film is light-exposed through the mask M3 anddeveloped, the photoresist film remaining at the B area is thinner thanthe photoresist film remaining at the A area. The photoresist film isabsent at the C area.

The slit pattern placed at the B area may be replaced by asemi-transparent pattern.

In case a negative photoresist film is used instead of the positivephotoresist film, the mask is structured to have a transparent patternplaced at the A area, and an opaque pattern placed at the C area.

Thereafter, as shown in FIG. 13, the portions of the insulating layer151 exposed through the photoresist patterns 116 and 117 are etchedwhile exposing the underlying common electrode 230.

As shown in FIG. 14, the photoresist patterns 116 and 117 are removedsuch that only the photoresist pattern 117 placed at the A area is leftover with a predetermined thickness.

The residual photoresist pattern 117 is removed so that insulatingpatterns 160 and 170 of different thickness are completed as shown inFIG. 8.

As described above, in the liquid crystal display according to thefourth preferred embodiment, the desired multi-domains are made usingfringe fields due to the thin organic insulating pattern withoutpatterning the common electrode of the color filter substrate so thatwide viewing angle can be obtained. Furthermore, the thick organicinsulating pattern functions as a spacer to maintain the cell gap in auniform manner. In this structure, the cell gap becomes so small thatenhances the response speed. Such organic insulating patterns are formedthrough one photolithography process while reducing the number ofrelevant processing steps.

FIGS. 15A through 23B sequentially illustrate the steps of fabricating aliquid crystal display with a thin film transistor array substrate and acolor filter substrate.

The process of fabricating the thin film transistor array substrate willbe first explained with reference to FIGS. 15A through 19B.

As shown in FIGS. 15A and 15B, a conductive layer of 1000-3000 Å isdeposited onto an insulating substrate 10 through sputtering, andpatterned through photolithography to thereby form a gate line assembly,and a storage capacitor line assembly. The gate line assembly includesgate lines 22, gate pads 24, and gate electrodes 26. The storagecapacitor line assembly includes storage capacitor lines 21, storagecapacitor electrodes 23, 25 and 27, and storage capacitor electrodeconnectors 28 and 29.

The storage capacitor line assembly may be formed in various shapes.

Thereafter, as shown in FIGS. 16A and 16B, a gate insulating layer of1500-5000 Å, an amorphous silicon layer of 500-1500 Å, animpurities-doped amorphous silicon layer of 300-600 Å are sequentiallydeposited onto the entire surface of the substrate 10. Theimpurities-doped amorphous silicon layer and the amorphous silicon layerare patterned through photolithography to thereby form an ohmic contactpattern 52 and a semiconductor pattern 42.

As shown in FIGS. 17A and 17B, a metallic conductive layer of 1500-3000Å is deposited onto the substrate 10, and patterned throughphotolithography to thereby form a data line assembly. The data lineassembly includes data lines 62, data pads 64, source electrodes 65, anddrain electrodes 66.

The ohmic contact layer 52 is etched using the source and the drainelectrodes 65 and 66 as a mask to thereby form an ohmic contact pattern55 connected to the source electrode 65, and an ohmic contact pattern 56connected to the drain electrode 66.

Then, as shown in FIGS. 18A and 18B, silicon nitride is deposited ontothe substrate 10 through chemical vapor deposition, or an organicinsulating film is spin-coated thereon to form a protective layer 70.

The protective layer 70 and the gate insulating layer 30 are patternedthrough photolithography to thereby form first contact holes 72 exposingthe drain electrodes 66, second contact holes 74 exposing the data pads64, and third contact holes 76 exposing the gate pads 24.

When the protective layer 70 is formed with the same material as thegate insulating layer 30, the two insulating layers 30 and 70 can beetched through only one photolithography process to form the contactholes 72, 74 and 76. Furthermore, in case the protective layer 70 isformed with a material different from the gate insulating layer, theprotective layer 70 is first patterned, and the underlying gateinsulating layer is etched using the protective layer as a mask to formthe contact holes 72, 74 and 76.

Thereafter, as shown in FIGS. 19A and 19B, an ITO or IZO-based layer of400-500 Å is deposited onto the entire surface of the substrate 10 withthe protective layer 70 through sputtering. The ITO or IZO-based layeris patterned through photolithography to thereby form pixel electrodes80 connected to the drain electrodes 66 through the first contact holes72, and subsidiary data and gate pads 84 and 86 connected to the dataand gate pads 64 and 24 through the second and third contact holes 74and 76.

Each pixel electrode 80 is patterned to be divided into a first portion81, or second portion 82 and a third 83. These are connected to eachother via the connectors 85 and 87. The pixel electrode 80 may be formedwith various shapes.

The process of fabricating the color filter substrate will be thenexplained with reference to FIGS. 20A through 23B.

As shown in FIGS. 20A and 20B, a black matrix 210 is formed on aninsulating substrate 200 with a double-layered structure ofchrome/chrome oxide, and color filters 220 of red, green and blue areformed at the black matrix 210.

As shown in FIG. 21, an over-coat layer 225 is formed on the colorfilter 220, and a common electrode 230 is formed on the entire surfaceof the substrate 200 of a transparent conductive material such as ITOand IZO.

Thereafter, as shown in FIG. 22, a positive photosensitive resin PR iscoated onto the entire surface of the substrate 200.

The photosensitive resin PR is used to form high molecular pillars andprotrusions. For instance, the photoresist resin PR is spin-coated ontothe substrate 10 at 400 rpm to a thickness of 3.8 μm.

Then, as shown in FIGS. 23A and 23B, protrusions 160 and high molecularpillars 170 are formed. The protrusions 160 and the high molecularpillars 170 may be formed at various portions of the substrate 200.

The protrusions 160 and the high molecular pillars 170 of differentheights may be simultaneously formed through one photolithographyprocess using one mask. The opening width of the mask pattern (calledthe “pattern width”) corresponding to the protrusion 160 is set to besmaller than the resolution of the light exposing device. The openingwidth of the mask pattern corresponding to the high molecular pillar 170is set to be larger than the resolution of the light exposing device.

It is preferable that the protrusion 160 bears a height of 1.0-1.2 μm,and the high molecular pillar 170 bears a height of 3.0-4.5 μm. Theamount of light exposure is controlled to be 300 mJ/cm². Furthermore,the width of the protrusion 160 is established to be 4-14 μm, and thatof the high molecular pillar 170 to be 15-45 μm.

The protrusion 160 and the high molecular pillar 170 then go throughhard baking for 40 minutes at a suitable temperature such that they beara predetermined strength. The height of the protrusion 160 and the highmolecular pillar 170 is altered depending upon the high bakingtemperature. The hard baking temperature is preferably established to be200-240° C.

The pattern width and the hard baking temperature suitable for obtainingthe desired height of the protrusion and the high molecular pillar areestablished in accordance with the experimental data and themathematical formulae 1, 2 and 3 to be described later.

Then, the combination of the thin film transistor array substrate andthe color filter substrate is made through the following steps.

A sealer is coated onto the periphery of the color filter substrate, andthe color filter substrate and the thin film transistor array substrateare arranged in an appropriate manner. The two substrates areheat-treated, and compressed against each other to attach together.

A liquid crystal material is injected between the two substrates.

The liquid crystal injection state of the liquid crystal display cell istested, and only good quality products are selected. Polarizing platesare attached to the liquid crystal cell to thereby complete a liquidcrystal display.

The reason that the protrusion and the high molecular pillar differentheights can be formed through controlling the pattern width and the hardbaking temperature will be now explained with reference to FIGS. 24through 28.

FIG. 24 is a graph illustrating the variation in height of the remainingphotosensitive resin pattern after the photolithography process as afunction of the pattern width and the hard baking temperature.

It is known from the graph of FIG. 24 that the narrower the patternwidth is, the lower the remaining photosensitive resin pattern heightbecomes.

This also relates to the resolution of the light exposing device. If thepattern width of the mask becomes smaller than the resolution of thelight exposing device, the less intense light enters the regions of thephotosensitive resin intercepted by the mask due to the resolution oflight so that the thickness of the photosensitive resin remaining afterthe development becomes smaller than the initial thickness.

Therefore, when the pattern width of the mask corresponding to theprotrusion becomes narrower and the pattern width of the maskcorresponding to the high molecular pillar becomes wider, the thicknessof the photosensitive resin sided with the pattern width smaller thanthe resolution of the light exposing device becomes smaller than theinitial thickness. In this way, the protrusion and the high molecularpillar of different heights can be formed in a simultaneous manner.

Meanwhile, when the photosensitive resin pattern goes through hardbaking at 200° C. or more, the height of the remaining photosensitiveresin pattern becomes further decreased at the narrow pattern width tothereby obtain the desired protrusion height. As shown in FIG. 24, thepattern width of 4 μm and hard-baked at 200° C., can obtain the heightof 1.3 μm suitable for the protrusion. Furthermore, the pattern width isestablished to be 15 μm or more with the above conditions, can obtainthe height of 3.0-3.5 μm suitable for the high molecular pillar.

FIG. 25 is an electron microscope photograph of a photosensitive resinremaining after the photolithography process. FIG. 26 is a conceptualview for mathematically inducing the sectional volume, width, andbreadth of the photosensitive resin shown in FIG. 25. FIG. 27 is aconceptual view illustrating the sectional profile of a photosensitiveresin after the hard baking process. FIG. 28 is a graph illustrating thevariation in height H of a photosensitive resin as a function of patternwidth.

As known from the photograph of FIG. 25, the remaining photosensitiveresin has an arc shape. From FIGS. 25 and 26, the following mathematicalformulas can be induced.H/W=(1−cos θ)/(2 sin θ)  (1)W/√A=(2 sin θ)/√(θ−sin θ cos θ)  (2)H/√A=(1−cos θ)/√(θ−sin θ cos θ)  (3)θ=cos⁻¹[{(W/2)² −H ²)/{(W/2)² +H ²}}  (4)

In the above mathematical formulae 1, 2, 3 and 4, θ is the taper angleof the photosensitive resin as a function of the hard bakingtemperature, H is the height of the photosensitive resin, W is thepattern width of the photosensitive resin related to the resolution, andA is the sectional volume of the photosensitive resin.

Meanwhile, if the photosensitive resin is hard-baked after the lightexposure and the development, the height of the remaining photosensitiveresin becomes further lowered. This can be confirmed at the graph ofFIG. 24, and expressed as the variation in θ that is dependent upon thehard baking temperature, as shown in FIG. 27. In the drawing, θ 1 is thesection of the photosensitive resin before the hard baking, and θ 2 isthe section of the photosensitive resin after the hard baking at asuitable temperature. That is, the section of the photosensitive resinremaining after the hard baking is altered from θ 1 to θ 2 whilechanging the pattern height.

Assuming that the value of θ is the same at a predetermined hard bakingtemperature, the variation in height H of the photosensitive resin as afunction of pattern width W at the respective values of 0 is applied tothe mathematical formulas. The results are illustrated in the graph ofFIG. 28.

This agrees to the experimental results illustrated in the graph of FIG.24.

It can be known from the above mathematical formulas that when twofactors among the height, width, sectional volume, and taper angle ofthe photosensitive resin are determined, the other two factors can beautomatically determined. Therefore, the desired height ofphotosensitive resin can be determined using the above mathematicalformulas.

In the structure according to the fifth preferred embodiment, theprotrusion pattern for the domain partitioning and the high molecularpillars for the cell gap fixation can be formed through one mask whilereducing the number of relevant processing steps and increasing theproductivity.

FIG. 29 is a plan view of a thin film transistor array substrate for aliquid crystal display according to a sixth preferred embodiment of thepresent invention. FIG. 30 is a cross sectional view of the thin filmtransistor array substrate taken along the XXX-XXX' line of FIG. 29.

A gate line assembly is formed on an insulating substrate 10 with a lowresistance metallic material based on aluminum, molybdenum, chrome ortitanium. The gate line assembly includes gate lines 22 proceeding inthe horizontal direction, gate pads 24 connected to ends of the gatelines 22 to receive gate signals from the outside and transmit them tothe gate lines, and gate electrodes 26 connected to the gate lines 22while forming thin film transistors.

The gate line assembly may be formed with a single or multiple-layeredstructure. When the gate line assembly is formed with a double-layeredstructure, at least one layer is preferably formed with a metallicmaterial bearing a low resistance characteristic.

A gate insulating layer 30 is formed on the insulating substrate 10 ofsilicon nitride while covering the gate line assembly.

A semiconductor pattern 42 is formed on the gate insulating layer 30with amorphous silicon while being overlapped with the gate electrodes26. Ohmic contact patterns 55 and 56 are formed on the semiconductorpattern 42 with amorphous silicon where n type impurities are doped athigh concentration.

A data line assembly is formed on the ohmic contact patterns 55 and 56and the gate insulating layer 30 with a metallic material bearing goodcontact characteristic with respect to the semiconductor layer and lowresistance characteristic such as molybdenum and molybdenum alloy.

The data line assembly includes data lines 62 proceeding in the verticaldirection, data pads 64 connected to ends of the data lines 62 toreceive data signals from the outside and transmit them to the datalines 62, source electrodes 65 protruded from the data lines 62 whilecontacting one side of ohmic contact pattern 55, and drain electrodes 66facing the source electrodes 65 while contacting the Other side of ohmiccontact pattern 56. The source and the drain electrodes 65 and 66construct the thin film transistors in association with the gateelectrodes 26.

An organic insulating pattern 70 is formed on the entire surface of thesubstrate 10 with the data line assembly as a protective layer based onan organic insulating material such as acrylic resin andbenzocyclobutene (BCB). The organic insulating pattern 70 has spacers 71protruded from the thin film transistors by the height of 4.5-5.5 μm,first contact holes 72 partially exposing the drain electrodes 66,second contact holes 74 exposing the data pads 64, and third contactholes 76 exposing the gate pads 24 together with the gate insulatinglayer 30. Except for the above components, the organic insulatingpattern 70 are evenly formed at the entire surface of the substrate 10by the height of 2-3 μm.

Pixel electrodes 82, subsidiary data pads 84, and subsidiary gate pads86 are formed on the protective layer 70 with IZO or ITO. The pixelelectrodes 82 are electrically connected to the drain electrodes 66through the first contact holes 72 to receive picture signals from thedata lines 62. The subsidiary gate and data pads 84 and 86 areelectrically connected to the gate and data pads 24 and 64 through thesecond and third contact holes 74 and 76.

A method for fabricating the thin film transistor array substrate willbe now explained with reference to FIGS. 31A, 31B, 32A, 32B, 33A, 33B,34A, 34B and 35.

As shown in FIGS. 31A and 31B, an aluminum-based layer having a lowresistance characteristic is deposited onto a substrate 10, andpatterned through photolithography to thereby form a gate line assembly.The gate line assembly includes gate lines 22, gate pads 24, and gateelectrodes 26.

Thereafter, as shown in FIGS. 32A and 32B, a gate insulating layer 30 isdeposited onto the substrate 10 with silicon nitride such that it coversthe gate line assembly.

A semiconductor layer and an impurities-doped semiconductor layer aresequentially deposited onto the gate insulating layer 30, and patternedthrough photolithography to thereby form an ohmic contact pattern 52 anda semiconductor pattern 42.

As shown in FIGS. 33A and 33B, a molybdenum-based layer bearing a goodcontact characteristic with respect to the semiconductor layer and a lowresistance characteristic is deposited onto the entire surface of thesubstrate 10, and patterned through photolithography to thereby form adata line assembly. The data line assembly includes data lines 62, datapads 64, source electrodes 65, and drain electrodes 66.

The island-shaped ohmic contact pattern 52 is etched using the sourceand the drain electrodes 65 and 66 as a mask to thereby form an ohmiccontact pattern 55 contacting the source electrodes 65, and an ohmiccontact pattern contacting the drain electrodes 66.

As shown in FIGS. 34A and 34B, an organic insulating pattern 70 isformed on the entire surface of the substrate 10 such that it hasspacers 71 protruded from the thin film transistors, first contact holes72 partially exposing the drain electrodes 66, second contact holes 74exposing the data pads 64, and third contact holes 76 contacting thegate pads together with the gate insulating layer 30.

The organic insulating pattern 70 can be formed through onephotolithography process using one mask. This technique will be nowexplained with reference to FIG. 35.

An organic insulating layer L is deposited onto the entire surface ofthe substrate 10 with a photosensitive organic insulating material. Thephotosensitive organic insulating material can be produced throughmixing a photosensitive material with an organic insulating materialsuch as acrylic resin and BCB.

The photosensitive organic insulating layer L is exposed to lightthrough a mask (not shown) having different light transmission. At thistime, a mask bearing a slit or lattice pattern or a semitransparent filmis used to control the light transmission. It is preferable that thepattern width should be smaller than the light decomposition capacity ofthe light exposing device. In the case of a semitransparent film, thinfilms of different light transmission or different thickness can be usedto control the light transmission.

In the photosensitive organic insulating layer L, the mask regionentirely exposed to light is placed at the area C where the firstcontact hole 72, the second contact hole 74 and the third contact holes76 are formed. The mask region entirely blocked from the light is placedat the area A where the spacers 71 are formed. The slit pattern or thesemitransparent film of the mask is placed at the remaining B area.

When the photosensitive organic insulating layer L is exposed to lightthrough such a mask, the high molecules at the C area are completelydecomposed, those at the B area are decomposed by a predeterminedthickness (for example, by half the thickness of the organic insulatinglayer), and those at the A area are not nearly decomposed. If the lightexposure is too long, all of the molecules are liable to be decomposed.

Instead of one mask, two masks may be used to expose the organicinsulating layer to light in a double manner.

For this purpose, the portions of the organic insulating layer at the Carea of the first, second and third contact holes 72, 74 and 76 areexposed to light through a first mask, and the portions of the organicinsulating layer at the B and C areas except for the A area where thespacers 71 are formed are exposed to light through a second mask. Then,the light-exposed organic insulating layer is developed to thereby forman organic insulating pattern 70. It is preferable that the lightexposure is preferably controlled at the light exposing based on thesecond mask to decompose the organic insulating layer only by apredetermined thickness.

When the selectively light-exposed organic insulating layer isdeveloped, the portions where the polymers are not decomposed are leftover, and the portions where the polymers are decomposed at some degreeare partially left over. Consequently, as shown in FIG. 34B, an organicinsulating pattern 70 is completed.

Of course, the organic insulating pattern 70 may be formed using anegative photosensitive organic insulating material where thelight-exposed portions are left over. In this case, the region of themask blocking light is placed at the C area where the first, second andthird contact holes 72, 74 and 76 are formed, and the region of the masktransmitting light is placed at the A area where the spacers 71 areformed. The slit pattern or the semitransparent film of the mask isplaced at the B area.

Thereafter, the gate insulating layer 30 is etched using the organicinsulating pattern 70 as a mask to thereby form third contact holes 76exposing the gate pads 24.

In order to heighten the light transmission of the organic insulatingpattern 70, the step of hardening the organic insulating pattern 70 maybe added.

As shown in FIGS. 29 and 30, an ITO or IZO-based layer is deposited ontothe substrate 10 with the organic insulating pattern 70, and patternedthrough photolithography to thereby form pixel electrodes 82 contactingthe drain electrodes 66 through the first contact holes 72, andsubsidiary gate and data pads 86 and 84 contacting the gate and datapads 24 and 64 through the second and third contact holes 76 and 74.

The subsequent processing steps are then made to thereby complete a thinfilm transistor array substrate.

As described above, in the thin film transistor array substrateaccording to the sixth preferred embodiment, the spacers are made duringthe photolithography process for forming the contact holes at theorganic insulating layer without separate processing steps, and thissimplifies the relevant processing steps.

FIG. 36 is a plan view of a thin film transistor array substrateaccording to a seventh preferred embodiment of the present invention,and FIGS. 37 and 38 are cross sectional views of the thin filmtransistor array substrate taken along the XXXVII-XXXVII′ line and theXXXVIII-XXXVIII′ of FIG. 36.

A gate line assembly is formed on an insulating substrate 10 with a lowresistance metallic material such as aluminum, molybdenum, chrome andtitanium. The gate line assembly includes gate lines 22 proceeding inthe horizontal direction, gate pads 24 connected to ends of the gatelines 22 to receive gate signals from outside and transmit them to thegate lines 22, and gate electrodes 26 connected to the gate lines 22.Storage capacitor electrodes 28 are arranged parallel to the gate lines22.

The storage capacitor electrodes 28 overlap storage capacitor conductivepatterns 68 connected to pixel electrodes 82 to be described later tothereby form storage capacitors. The storage capacitors enhance theelectric potential storage capacity of the pixels. In case sufficientstorage capacity is obtained through the overlapping of the pixelelectrodes 82 and the gate lines, the storage capacitor electrodes 28may be omitted.

The gate line assembly may be formed with a single or multiple-layeredstructure. In case the gate line assembly is formed with adouble-layered structure, at least one layer is preferably formed with alow resistance metallic material.

A gate insulating layer 30 is formed on the insulating substrate 10 withan insulating material such as silicon nitride while covering the gateline assembly.

Semiconductor patterns 42 and 48 are formed on the gate insulating layer30 with a semiconductor material such as amorphous silicon, and ohmiccontact patterns 55, 56 and 58 are formed on the semiconductor patterns42 and 48 with amorphous silicon where impurities are doped.

A data line assembly is formed on the ohmic contact patterns 55, 56 and58 with a low resistance metallic material bearing good contactcharacteristic with the semiconductor layer, such as molybdenum.

The data line assembly includes data lines 62 proceeding in thehorizontal direction while crossing over the gate lines 22, data pads 64connected to ends of the data lines 62 to receive data signals from theoutside and transmit them to the data lines 62, source electrodes 65protruded from the data lines 62 while contacting one side of the ohmiccontact pattern 55, and drain electrodes 66 facing the source electrodes65 while contacting the other side of the ohmic contact pattern 56.Storage capacitor conductive patterns 68 are placed over the storagecapacitor electrodes 28.

The semiconductor patterns 42 and 48 include a thin film transistorsemiconductor pattern 42, and a storage capacitor semiconductor pattern48. The semiconductor patterns 42 and 48 have the same shape as the dataline assembly and the ohmic contact patterns 55, 56 and 58 except forthe channel region between the source and the drain electrodes 65 and66. That is, the storage capacitor semiconductor pattern 48 has the sameshape as the storage capacitor conductive pattern 68 and the storagecapacitor ohmic contact pattern 58. The thin film transistorsemiconductor pattern 42 has the same shape as the data lines 62, thedata pads 64, and the source and drain electrodes 65 and 66 except thatit further includes the channel portion between the source and the drainelectrodes 65 and 66.

The ohmic contact patterns 55, 56 and 58 lower the contact resistancebetween the underlying semiconductor patterns 42 and 48 and theoverlying data line assembly while bearing the same shape as the dataline assembly. The first ohmic contact pattern 55 contacts the datalines 62, the data pads 64 and the source electrodes 65, the secondohmic contact pattern 56 contacts the drain electrodes 66, and the thirdohmic contact pattern 58 contacts the storage capacitor conductivepattern 68.

An organic insulating pattern 70 is formed on the entire surface of thesubstrate 10 with the data line assembly of an organic insulatingmaterial such as acrylic resin and BCB. The organic insulating pattern70 has spacers 71 protruded from the thin film transistors by the heightof 4.5-5.5 μm, first contact holes partially exposing the drainelectrodes 66, second contact holes 74 exposing the data pads 64, thirdcontact holes 76 exposing the gate pads 24 together with the gateinsulating layer 30, and fourth contact holes exposing the storagecapacitor conductive pattern 68. Except for the above components, theorganic insulating pattern 70 is evenly formed on the entire surface ofthe substrate 10 by the height of 2-3 μm.

Pixel electrodes 82, and subsidiary gate and data pads 86 and 84 areformed on the organic insulating pattern 70 with IZO or ITO. The pixelelectrodes 82 contact the drain electrodes 66 and the storage capacitorconductive pattern 68 through the first and fourth contact holes 72 and78. The subsidiary gate and data pads 86 and 84 contact the gate anddata pads 24 and 64 through the second and third contact holes 74 and76.

A method for fabricating the thin film transistor array substrate willbe now explained with reference to FIGS. 39A through 47B.

As shown in FIGS. 39A, 39B and 39C, an aluminum-based layer bearing alow resistance is deposited onto a substrate 10, and patterned throughphotolithography to thereby form a gate line assembly. The gate lineassembly includes gate lines 22, gate pads 24, gate electrodes, and astorage capacitor conductive pattern 28.

A gate insulating layer 30 is deposited onto the substrate 10 with aninsulating material such as silicon nitride while covering the gate lineassembly.

As shown in FIGS. 40A, 40B and 40C, a semiconductor layer, animpurities-doped semiconductor layer and a metallic layer aresequentially deposited onto the gate insulating layer, and patternedthrough photolithography to thereby form semiconductor patterns 42 and48, ohmic contact patterns 55, 56 and 58, and a data line assembly. Thedata line assembly includes data lines 62, data pads 64, sourceelectrodes 65, drain electrodes 66, and storage capacitor electrodes 68.It is preferable that the metallic layer for the data line assembly isbased on a low resistance metallic material bearing good contactcharacteristic with respect to the semiconductor layer such asmolybdenum.

The data line assembly has the same outline as the underlying ohmiccontact patterns 55, 56 and 58 that have in turn the same outline as theunderlying semiconductor patterns 42 and 48 for the thin filmtransistors and the storage capacitors. The thin film transistorsemiconductor pattern 42 has the same shape as the data lines 62, thedata pads 64, and the source and drain electrodes 65 and 66 except thatit further has the channel portion between the source and the drainelectrodes 65 and 66.

The data line assembly, the ohmic contact patterns 55, 56 and 58, andthe semiconductor patterns 42 and 48 may be formed using only one mask.This technique will be now explained with reference to FIGS. 41A through45B.

As shown in FIGS. 41A and 41B, a semiconductor layer 40, animpurities-doped semiconductor layer 50 are sequentially deposited ontothe gate insulating layer 30 through chemical vapor deposition, andsubsequently, a metallic layer 60 is deposited onto the impurities-dopedsemiconductor layer 50.

Thereafter, as shown in FIGS. 42A and 42B, a photoresist film is coatedonto the metallic layer 60. The photoresist film is exposed to lightthrough a mask (not shown), and developed to thereby form first andsecond photoresist patterns 112 and 114. The first photoresist pattern112 is placed at the data line area A, and the second photoresistpattern 114 is placed at the channel area C between the source and thedrain electrodes 65 and 66. The photoresist film at the remaining area Bis all removed. The first photoresist pattern 112 has a thickness largerthan the second photoresist pattern 114. The thickness ratio of thesecond photoresist pattern 114 to the first photoresist pattern 112should be determined depending upon the processing conditions at thesubsequent etching. The thickness ratio is preferably established to be½.

The photoresist pattern of different thickness is formed using a mask ofdifferent light transmission. In order to control the lighttransmission, the mask is provided with a slit or lattice pattern or asemitransparent film. It is preferable that the pattern width should besmaller than the decomposition capacity of the light exposing device. Inthe case of a semitransparent film, a thin film of different lighttransmission or thickness can be used.

The photoresist film is exposed to light through such a mask, the highmolecules at the area C directly exposed to light are completelydecomposed, those at the area B corresponding to the slit pattern or thesemitransparent film are decomposed at some degree, and those at thearea A blocked from the light are not nearly decomposed. If the lightexposure is too long, all of the molecules are liable to be decomposed.

When the selectively light-exposed photoresist film is developed, theportions where the molecules are not decomposed are left over so thatthe thickness of the photoresist pattern blocked from light is differentfrom the portions partially exposed to light.

As shown in FIGS. 43A and 43B, the metallic layer 60 at the B area isetched using the photoresist patterns 112 and 114 as a mask whileexposing the underlying impurities-doped semiconductor layer 50.

Consequently, the metallic patterns 67 and 68 placed at the channel areaC and the data line assembly area A are left over, and the metalliclayer at the remaining area B is removed while exposing the underlyingimpurities-doped semiconductor layer 50. The metallic pattern 68 becomesa storage capacitor conductive pattern, and the metallic pattern 67becomes a data line assembly where the source and the drain electrodes65 and 66 are not yet separated.

Thereafter, as shown in FIGS. 44A and 44B, the impurities-dopedsemiconductor layer 50 at the B area and the underlying semiconductorlayer 40 are simultaneously removed through dry etching together withthe second photoresist pattern 114. At this time, the etching should bemade in condition that the photoresist patterns 112 and 114, theimpurities-doped semiconductor layer 50 and the semiconductor layer 40are simultaneously etched while not etching the gate insulating layer30. It is preferable that the etching ratios with respect to thephotoresist patterns 112 and 114 and the semiconductor layer 40 arenearly the same. For instance, the two layers can be etched by nearlythe same thickness using a mixture of SF₆ and HCI or a mixture of SF₆and O₂

In case the etching ratios with respect to the photoresist patterns 112and 114 and the semiconductor layer 40 are the same, the thickness ofthe second photoresist pattern 114 should be the same as or smaller thanthe sum in thickness of the semiconductor layer 40 and theimpurities-doped semiconductor layer 50.

Consequently, the second photoresist pattern 114 at the channel area Cis removed while exposing the underlying metallic pattern 67, and theimpurities-doped semiconductor layer 50 and the semiconductor layer 40at the B area are removed while exposing the underlying gate insulatinglayer 30. Meanwhile, the first photoresist pattern 112 at the data lineassembly area A is also etched while being reduced in thickness.

In this process, the semiconductor patterns 42 and 48 for the thin filmtransistors and the storage capacitors are completed.

Furthermore, an ohmic contact pattern 57 is formed on the thin filmtransistor semiconductor pattern 42 with the same outline, and an ohmiccontact pattern 58 is formed on the storage capacitor semiconductorpattern 48 with the same outline.

The second photoresist pattern remaining on the metallic pattern 67 atthe channel area c is removed through ashing.

Thereafter, as shown in FIGS. 45A and 45B, the metallic pattern 67 atthe channel area C and the underlying ohmic contact pattern 57 areetched using the first photoresist pattern 112 as a mask.

At this time, the semiconductor pattern 42 may be partially etched whilebeing reduced in thickness. The first photoresist pattern 112 is alsoetched by a predetermined thickness. The etching should be made incondition that the gate insulating layer 30 is not etched. The thicknessof the first photoresist pattern 112 is preferably so large as toprevent the underlying data line assembly from being exposed to theoutside through the etching.

In this process, the source and the drain electrodes 65 and 66 areseparated from each other. That is, the data lines 62, the sourceelectrodes 65 and the drain electrodes 68 are completed together withthe underlying ohmic contact patterns 55, 56 and 58.

Thereafter, as shown in FIGS. 46A, 46B and 46C, the first photoresistpattern 112 remaining at the substrate 10 is removed through ashing.

An organic insulating pattern 70 is then formed on the entire surface ofthe substrate 10 such that it has spacers 71 protruded from the thinfilm transistors, first contact holes 72 partially exposing the drainelectrodes 66, second contact holes 76 exposing the data pads 64, thirdcontact holes 74 exposing the gate pads 24 together with the gateinsulating layer 30, and fourth contact holes 78 exposing the storagecapacitor conductive pattern 68.

The organic insulating pattern 70 may be formed through onephotolithography process. This technique will be now explained withreference to FIGS. 47A and 47B.

An organic insulating layer L is deposited onto the entire surface ofthe substrate 10 with the data line assembly based on a photosensitiveorganic insulating material. The photosensitive organic insulatingmaterial can be prepared through mixing a photosensitive material withacrylic resin or BCB.

Thereafter, the photosensitive organic insulating layer L is selectivelyexposed to light through a mask (not shown) of different lighttransmission.

In the photosensitive organic insulating layer L, the region of the maskdirectly exposed to light is placed at the C area where the firstthrough fourth contact holes 72, 74, 76 and 78 are formed, the region ofthe mask blocked from light is placed at the A area where the spacers 71are formed, and the slit pattern or the semitransparent film of the maskis placed at the remaining B area.

When the photosensitive organic insulating layer L is exposed to lightthrough such a mask, the molecules at the C area are completelydecomposed, those at the B area are decomposed by a predeterminedthickness, and those at the A area are barely decomposed. In case thelight exposure is too long, all of the molecules are liable to bedecomposed.

The light exposing with respect to the organic insulating layer may bemade using two masks.

For this purpose, the portions of the organic insulating layer at the Carea where the first through fourth contact holes are formed are exposedto light using a first mask, and the portions at the B and C areasexcept for the A area where the spacers 71 are formed are exposed tolight using a second mask. The organic insulating layer is thendeveloped to form an organic insulating pattern 70. The amount of lightexposure should be controlled such that the organic insulating layer isnot completely decomposed.

When the selectively light-exposed organic insulating layer isdeveloped, only the portions thereof where the molecules are notdecomposed are left over. Consequently, as shown in FIGS. 46B and 46C,the organic insulating pattern 70 of different thickness is completed.

Of course, the organic insulating pattern 70 may be formed using anegative photosensitive organic insulating material where thelight-exposed portions are left over. In this case, the region of themask intercepted from light is placed at the C area where the firstthrough fourth contact holes 72, 74, 76 and 78 are formed, and theregion of the mask exposed to light is placed at the A area where thespacers 71 are formed. The slit pattern or the semitransparent film ofthe mask is placed at the B area.

Thereafter, the gate insulating layer 30 is etched using the organicinsulating pattern 70 as a mask to thereby form third contact holes 76exposing the gate pads 24.

In order to heighten the light transmission of the organic insulatingpattern 70, the step of hardening the organic insulating pattern 70 maybe additionally made.

As shown in FIGS. 36, 37 and 38, an ITO or IZO-based layer is depositedonto the substrate 10 with the organic insulating pattern 70, andpatterned through photolithography to thereby form pixel electrodes 82contacting the drain electrodes 66 and the storage capacitor conductivepattern 68 through the first and fourth contact holes 72 and 78, andsubsidiary gate and data pads 86 and 84 contacting the gate and datapads 24 and 64 through the second and third contact holes 76 and 74.

The subsequent processing steps are then made to thereby complete a thinfilm transistor array substrate.

As described above, in the thin film transistor array substrateaccording to the seventh preferred embodiment, the spacers are madeduring the photolithography process for forming the contact holes at theorganic insulating layer without requiring separate processing steps,and this simplifies the relevant processing steps.

FIG. 48 is a plan view of a thin film transistor array substrateaccording to an eighth preferred embodiment of the present invention,and FIG. 49 is a cross sectional view of the thin film transistor arraysubstrate taken along the XXXXIX-XXXXIX′ line of FIG. 48.

The basic structure of the thin film transistor array substrateaccording to the eighth preferred embodiment is the same as that relatedto the fifth preferred embodiment except for the pattern shape of theprotective layer 70. In the fifth preferred embodiment, the spacers areformed at the color filter substrate. However, in this preferredembodiment, the spacers 71 are formed at the thin film transistor arraysubstrate together with the protective layer 70.

As shown in FIG. 49, the protective layer 70 based on an organicinsulating material has spacers 71 protruded from the thin filmtransistors by the height of 4.5-5.5 μm, first contact holes 72partially exposing the drain electrodes 66, second contact holes 74exposing the data pads 64, and third contact holes 76 exposing the gatepads 24 together with the gate insulating layer 30. Except for the abovecomponents, the protective layer 70 is evenly formed on the entiresurface of the substrate 10 by the height of 2-3 μm.

Pixel electrodes each with patterned electrode portions 81, 82, 83, 85and 87, and subsidiary gate and data pads 86 and 84 are formed on theprotective layer 70. The pixel electrodes contact the drain electrodes66 through the first contact holes 72, and the subsidiary gate and datapads 86 and 84 contact the gate and data pads 24 and 64 through thesecond and third contact holes 74 and 76.

The above-structured thin film transistor array substrate is combinedwith the color filter substrate where a common electrode (not shown)with an opening pattern (indicated by the dotted line in FIG. 48) tothereby form a liquid crystal display. In such a liquid crystal display,the pixel electrode pattern and the opening pattern of the commonelectrode partition the liquid crystal so that a plurality of liquidcrystal domains are formed at one pixel region, realizing wide viewingangle.

The method for fabricating the thin film transistor array substrate isthe same as that related to the fifth preferred embodiment except forthe process of forming the protective layer 70.

The process of forming the protective layer 70 with the spacers 71 andthe contact holes 72, 74 and 76 is the same as that related to the sixthand seventh preferred embodiments.

As described above, since the spacers are formed during the process ofpatterning the organic insulating layer to form contact holes, theprocessing steps of forming the spacers such as the steps of coating aphotoresist film, light-exposing the photoresist film and developing thephotoresist film can be omitted, and this significantly reduces thenumber of relevant processing steps.

As the spacers are fixed to the substrates, the picture quality isenhanced while minimizing variation in the brightness. Furthermore, asthe spacers are formed together with the organic insulating pattern, theprocessing steps can be simplified.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A liquid crystal display, comprising: a first substrate and a secondsubstrate; a liquid crystal layer being sandwiched between the first andsecond substrates; a gate line and a data line provided on the firstsubstrate; a plurality of pixel electrodes provided on the firstsubstrate; a plurality of protrusions disposed on the second substrate,the protrusions comprising bodies that are arranged obliquely withrespect to the gate line and branches extending from the bodies in afirst direction along edges of the pixel electrodes; and a spacerarranged on the gate line and extending in a second direction from whereone of the bodies meets one of the edges of the pixel electrodes, thesecond direction being opposite the first direction.